The present invention relates generally to the use of certain proteins of known amino acid sequence which stimulate neuron growth and differentiation, and the use of these proteins in animals to influence and mitigate disease states associated with neuron death.
A protein from rat heart that controls the development of neurons has been purified and characterized (Fukada, Proc. Natl. Acad. Sci. USA 82:8495, 1985). This protein, secreted into the medium of cultured heart cells, was found to induce cultured sympathetic neurons to synthesize acetylcholine and form cholinergic synapses, while suppressing catecholamine synthesis and noradenergic function. The amino acid sequence of this protein (CDF) was deduced and compared the sequence information to that available on the computer data base for all known proteins. It was discovered that the gene for the mouse version of the protein had been published (Gearing et al., EMBO J. 6:3995, 1987). The protein expressed by this gene, called LIF, for leukemia inhibitory factor, has been disclosed in European Patent Application Publication No. 0285448, published May 10, 1988, based an Application No. 88302962.1, the disclosure of which is expressly incorporated herein by reference.
The LIF protein will also be referred to herein as CDF, and is also known as human macrophage differentiation inducing factor (DIF).
The term "differentiation factor" is used because the protein controls phenotypic choices in these neurons without affecting their survival or growth.
CDF converts adrenal medullary cells to the production of acetylcholine (Doupe et al., J. Neuroscience 5:2119, 1985). This discovery implies that the protein may enhance acetylcholine synthesis in a variety of neurons, including those in the central nervous system when appropriately administered.
The importance of CDF is seen as three-fold. First, this protein can stimulate the growth of neurons. The ability to increase neuron vitality and to inhibit neuron death is of great importance in the treatment of diseases such as Alzheimer's and amyotrophic lateral sclerosis (ALS).
Secondly, it can be injected into the circulation or the central nervous system to alter the chemical balance of inhibitory versus excitatory nerves. The traditional method of doing this is to use pharmacological agents that block neurotransmitter receptors, or the enzymes that break down transmitters. CDF can be used to alter transmitters by changing the rate at which they are synthesized, by enhancing the rates of transcription of the messages for specific enzymes that synthesize transmitters. The transmitter balance in the case of sympathetic neurons is acetylcholine (which slows the heart beat) versus catecholamines (which speed the heart beat). In the central nervous system, acetylcholine is a transmitter of great interest in the pathology of Alzheimer's disease and ALS, the loss of this transmitter being one of the cardinal signs of these diseases.
Thirdly, the ability of CDF to convert adrenal medullary cells to acetylcholine production may be beneficial in providing a source of acetylcholine producing cells for autotransplantation to the brain as an alternative procedure for the treatment of Alzheimer's disease and other disease states associated with acetylcholine deficiency. There are a number of advantages in using a patient's own tissue for grafts. Autografts alleviate the need for immunosuppression, and the ethical, legal and availability problems associated with the use of fetal tissue are avoided. In addition, adrenal autografts with Parkinsonism have yielded a number of positive results. Thus, CDF is of potential medical benefit, and it is believed that the present invention represents a significant advance in the art.